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Tatsuhiko Miyagawa
and 96 contributors


Plack::Middleware::AccessLog - Logs requests like Apache's log format


  # in app.psgi
  use Plack::Builder;

  builder {
      enable "Plack::Middleware::AccessLog", format => "combined";


Plack::Middleware::AccessLog forwards the request to the given app and logs request and response details to the logger callback. The format can be specified using Apache-like format strings (or combined or common for the default formats). If none is specified combined is used.

This middleware uses calculable Content-Length by checking body type, and cannot log the time taken to serve requests. It also logs the request before the response is actually sent to the client. Use Plack::Middleware::AccessLog::Timed if you want to log details after the response is transmitted (more like a real web server) to the client.

This middleware is enabled by default when you run plackup as a default development environment.


  enable "Plack::Middleware::AccessLog",
      format => '%h %l %u %t "%r" %>s %b "%{Referer}i" "%{User-agent}i"';

Takes a format string (or a preset template combined or custom) to specify the log format. This middleware uses Apache::LogFormat::Compiler to generate access_log lines. See more details on perldoc Apache::LogFormat::Compiler

   %%    a percent sign
   %h    REMOTE_ADDR from the PSGI environment, or -
   %l    remote logname not implemented (currently always -)
   %u    REMOTE_USER from the PSGI environment, or -
   %t    [local timestamp, in default format]
   %r    REQUEST_METHOD, REQUEST_URI and SERVER_PROTOCOL from the PSGI environment
   %s    the HTTP status code of the response
   %b    content length of the response
   %T    custom field for handling times in subclasses
   %D    custom field for handling sub-second times in subclasses
   %v    SERVER_NAME from the PSGI environment, or -
   %V    HTTP_HOST or SERVER_NAME from the PSGI environment, or -
   %p    SERVER_PORT from the PSGI environment
   %P    the worker's process id
   %m    REQUEST_METHOD from the PSGI environment
   %U    PATH_INFO from the PSGI environment
   %q    QUERY_STRING from the PSGI environment
   %H    SERVER_PROTOCOL from the PSGI environment

Some of these format fields are only supported by middleware that subclasses AccessLog.

In addition, custom values can be referenced, using %{name}, with one of the mandatory modifier flags i, o or t:

   %{variable-name}i    HTTP_VARIABLE_NAME value from the PSGI environment
   %{header-name}o      header-name header in the response
   %{time-format]t      localtime in the specified strftime format
  my $logger = Log::Dispatch->new(...);
  enable "Plack::Middleware::AccessLog",
      logger => sub { $logger->log(level => 'debug', message => @_) };

Sets a callback to print log message to. It prints to the psgi.errors output stream by default.


Tatsuhiko Miyagawa

Masahiro Nagano


Apache::LogFormat::Compiler, http://httpd.apache.org/docs/2.2/mod/mod_log_config.html Rack::CustomLogger